1) Technical Field
The subject invention relates to a beverage filling machine for filling a container with a liquid material and having a moveable vent tube for venting gases from the container during the filling process.
2) Description of the Prior Art
Filling mechanisms used for filling containers, such as cans, jars, or bottles, with a beverage, such as carbonated drinks, juices, water or the like, as are well known in the art. Conventional filling mechanisms feed the containers into a star wheel conveyor which individually positions each container on a rotating turntable below a valve assembly of an individual filling machine. The container moves into sealing engagement with the valve assembly by either moving the container upwardly or by lowering the valve assembly. Modem filling machines are known in the art as counter pressure filling machines as is discussed below. There may be as many as 120 individual filling machines disposed circumferentially around the turntable. The filling machines typically include a support housing having an inner fluid chamber or ring bowl disposed above the valve assembly. The ring bowl is usually annular and contains the liquid or beverage for filling the containers and has a space above the liquid for a pressurized inert gas such as carbon dioxide or nitrogen. This space above the liquid is known as the headspace. A common storage tank or reservoir feeds the ring bowl with the required liquid and gas.
In the typical filling operation, the container, which is sealed against the valve assembly, is initially purged with the inert gas from the ring bowl for a predetermined time in order to flush air and other impurities from the container. A vent tube is introduced into the container to accomplish this and other operations. Specifically, the vent tube moves from a non-use position raised above the container to a filling position disposed within the container. The liquid is filled into the container from the ring bowl while the gas from the container vents through the vent tube into the headspace. The liquid will at least partially rise into the vent tube during the filling of the container. The gas pressure in the container and the ring bowl are equalized when filling begins. This is what is known as counter pressure which allows the liquid to flow into the container solely under the influence of gravity. After the container is filled to a desired level, the vent tube rises out of the container. Finally, gas is released from the top of the container to the atmosphere by an process commonly known as "snifting".
The beverage filling industry continuously strives for machinery and methods which facilitate rapid, economical, efficient, and sterile filling of containers. As discussed above, it is common for the vent tube to move in and out of the container during the filling operation. The prior art devices typically utilize complicated mechanical mechanisms for moving the vent tube between the non-use and filling positions during the filling operation. An example of one such device is disclosed in U.S. Pat. No. 3,633,635 to Kaiser. These known devices can be expensive and difficult to maintain. Such mechanical devices could also significantly jeopardize the sterile environment of the filling machines.
A pneumatic device for moving the vent tube has also been contemplated by the prior art. U.S. Pat. No. 3,595,280 to Fissel discloses such a device. The Fissel filling valve utilizes a single air input port for injecting air pressure into a chamber to force a piston downwardly. A spring continuously pushes the piston upward against the force of the air pressure. Hence, the downward movement of the vent tube is controlled by the air pressure and the upward movement is controlled by the air pressure and the spring. This movement of the vent tube, however, could be very difficult to control. Specifically, the desired displacement of the vent tube is dependent upon the biasing force of the spring. Over time the biasing force of the spring may change which would affect the operation of the vent tube. In addition, the pressure within the chamber would preferably be released slowly in order to slowly raise the vent tube. The slow exhausting of the chamber could be difficult manage.